Display device

ABSTRACT

A display device includes a touch panel; a display panel under the touch panel and displaying an image; a piezoelectric element under the touch panel and including an upper electrode, a lower electrode and a piezoelectric layer; and a rectifying circuit connected to the piezoelectric element.

This application is a continuation of U.S. patent application Ser. No.16/710,201, filed on Dec. 11, 2019, which claims priority from and thebenefit of Korean Patent Application No. 10-2018-0170856, filed on Dec.27, 2018. Each of the above prior U.S. and Korean patent applications ishereby incorporated herein by reference in its entirety for all purposesas if fully set forth herein.

BACKGROUND Technical Field

The present disclosure relates to a display device, and moreparticularly, to a display device having a piezoelectric element.

Discussion of the Related Art

An electroluminescent display device may be a flat panel display device.An electroluminescent display device has a wide viewing angle ascompared with a liquid crystal display device because it isself-luminous, thin, light weight, and low in power consumption becausea backlight unit is not necessary. In addition, an electroluminescentdisplay device is driven by low voltages of direct current (DC) and hasa fast response time. An electroluminescent display device is alsoresistant to external impacts and may be used in a wide range oftemperatures because its components are solids. An electroluminescentdisplay device may also be manufactured at low cost.

An electroluminescent display device has been applied to variousdevices. Especially, the electroluminescent display device has beenwidely applied to portable devices such as smartphones, multimediadevices or table PCs. By the way, since these portable devices aresupplied with power sources through a battery, there is a limitation insupplying the power sources.

SUMMARY

Accordingly, embodiments of the present disclosure are directed to adisplay device that substantially obviates one or more of the problemsdue to limitations and disadvantages of the related art.

An aspect of the present disclosure is to provide a display device thatis capable of improving the power efficiency.

Additional features and aspects will be set forth in the descriptionwhich follows, and in part will be apparent from the description, or maybe learned by practice of the inventive concepts provided herein. Otherfeatures and aspects of the inventive concepts may be realized andattained by the structure particularly pointed out in the writtendescription, or derivable therefrom, and claims hereof as well as theappended drawings.

To achieve these and other aspects of the inventive concepts, asembodied and broadly described herein, a display device comprises atouch panel; a display panel under the touch panel and displaying animage; a piezoelectric element under the touch panel and including anupper electrode, a lower electrode and a piezoelectric layer; and arectifying circuit connected to the piezoelectric element.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory, andare intended to provide further explanation of the inventive concepts asclaimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this application, illustrate embodiments of the disclosure andtogether with the description serve to explain various principles of thepresent disclosure. In the drawings:

FIG. 1 is a cross-sectional view schematically illustrating a displaydevice according to a first embodiment of the present disclosure;

FIG. 2 is a circuit diagram of a rectifying circuit according to anembodiment of the present disclosure;

FIG. 3 is a schematic plan view of a rectifying circuit according to theembodiment of the present disclosure;

FIG. 4 is a plan view schematically illustrating a display deviceaccording to the fist embodiment of the present disclosure;

FIG. 5 is a schematic cross-sectional view of a display device includinga piezoelectric element according to the first embodiment of the presentdisclosure and corresponds to the line V-V′ of FIG. 4 ;

FIG. 6 and FIG. 7 are plan views schematically illustrating electrodestructures of a piezoelectric element according to the first embodimentof the present disclosure;

FIG. 8 is a cross-sectional view schematically illustrating a displaydevice according to a second embodiment of the present disclosure;

FIG. 9 is a cross-sectional view schematically illustrating a displaydevice according to a third embodiment of the present disclosure; and

FIG. 10 is a cross-sectional view schematically illustrating a displaydevice according to a fourth embodiment of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to example embodiments of thedisclosure, which are illustrated in the accompanying drawings.

First Embodiment

FIG. 1 is a cross-sectional view schematically illustrating a displaydevice according to a first embodiment of the present disclosure.

In FIG. 1 , the display device according to the first embodiment of thepresent disclosure includes a display panel 100, a piezoelectric element200, a touch panel 300, a polarizing plate 400 and a cover window 500.

Here, the display panel 100 may be an electroluminescent display panel.More particularly, the display panel 100 may include a light-emittingdiode De on a substrate 110 and an encapsulation layer 190 on thelight-emitting diode De. The light-emitting diode De includes a firstelectrode 160, a second electrode 180, and a light-emitting layer 180between the first and second electrodes 160 and 180.

However, the present disclosure is not limited thereto, and the displaypanel 100 may be a liquid crystal display panel including a liquidcrystal capacitor.

The piezoelectric element 200 is disposed on the display panel 100. Thepiezoelectric element 200 includes a first buffer layer 210, a lowerelectrode 220, a piezoelectric layer 230, an upper electrode 240, and asecond buffer layer 250.

The first and second buffer layers 210 and 250 may be formed of atransparent insulating material. For example, the first and secondbuffer layers 210 and 250 may be formed of an inorganic insulatingmaterial such as silicon oxide (SiO₂) or silicon nitride (SiNx).Alternatively, the first and second buffer layers 210 and 250 may beformed of an organic insulating material such as photo acryl, but is notlimited thereto.

The lower electrode 220 and the upper electrode 240 may be formed of atransparent conductive material. For example, the lower electrode 220and the upper electrode 240 may be formed of indium tin oxide (ITO) orindium zinc oxide (IZO), but is not limited thereto.

The piezoelectric layer 230 may be formed of a piezoelectric materialthat generates electrical energy by causing deformation of the materialdue to external mechanical energy. The piezoelectric material may be atransparent piezoelectric polymer.

For example, the piezoelectric polymer may be PVDF(polyvinylidenefluoride), P(VDF-TrFE)(polyvinylidene fluoride-co-trifluoroethylene),P(VDF-TrFE-CFE)(poly(vinylidenefluoride-co-triluoroethylene-chlorofluoroethylene),P(VDF-TrFE-CTFE)(poly(vinylidene fluoride-co-triluoroethylene-chlorotrifluoroethylene), PVDF doped with carbonnanotubes, or a phosphazene-based polymer, but is not limited thereto.Here, poly bis(trifluoroethoxy) phosphazene may be used as thephosphazene-based polymer.

Next, the touch panel 300 is disposed on the piezoelectric element 200.The touch panel 300 may be a mutual capacitance type in which atransmitting line and a receiving line are independently formed and achange in capacitance between the transmitting line and the receivingline is detected according to a touch. However, the present disclosureis not limited thereto.

The polarizing plate 400 may be disposed on the touch panel 300. Thetouch panel 300 may be a circular polarizing plate which includes alinear polarizer and a quarter wave plate and changes linearly polarizedlight into circularly polarized light and circularly polarized lightinto linearly polarized light. The polarizing plate 400 may improve thecontrast ratio by blocking external light from being outputted afterbeing reflected at the display panel 100.

The cover window 500 is disposed on the polarizing plate 400. The coverwindow 500 protects the display panel 100 from the external impacts. Thecover window 500 may be attached to an upper portion of the displaypanel 100, more particularly, to the polarizing plate 400 through anadhesive layer (not shown). The cover window 500 may be formed of glassor plastic, but is not limited thereto.

As described above, in the display device according to the firstembodiment of the present disclosure, an energy harvesting element forreproducing energy can be implemented by providing the piezoelectricelement 200 between the display panel 100 and the touch panel 300,generating electrical energy from an external force by a touch, andcharging a battery with the generated electrical energy.

It is preferable that the piezoelectric element 200 is disposed close tothe cover window 500 in order to improve the energy harvestingefficiency.

At this time, in the piezoelectric element 200, a rectifying circuit isneeded to store the generated electrical energy into the battery. Therectifying circuit is illustrated in FIG. 2 and FIG. 3 .

FIG. 2 is a circuit diagram of a rectifying circuit according to anembodiment of the present disclosure, and FIG. 3 is a schematic planview of a rectifying circuit according to the embodiment of the presentdisclosure.

In FIG. 2 and FIG. 3 , the rectifying circuit according to theembodiment of the present disclosure may be a bridge circuit connectingfour diodes. Here, input terminals are connected to the piezoelectricelement 200, and output terminals are connected to the battery, therebychanging alternating current input of the piezoelectric element 200 intodirect current output.

In the rectifying circuit, P-type semiconductor and/or N-typesemiconductor of the diode may be formed through the same process as asemiconductor layer of the display panel 100, and an anode and a cathodeof the diode may be formed through the same process as a gate line or adata line of the display panel 100.

FIG. 4 is a plan view schematically illustrating a display deviceaccording to the fist embodiment of the present disclosure. Descriptionwill be made with reference to FIG. 1 and FIG. 4 .

In FIG. 1 and FIG. 4 , a display area A1 displaying an image and anon-display area A2 surrounding the display area A1 are defined on asubstrate 110 of the display panel 100.

In the display area A1 on the substrate 110, gate lines GL are formedalong a first direction, and data lines DL are formed along a seconddirection crossing the first direction. In addition, although not shownin the figures, one or more thin film transistors, one or morecapacitors and a light-emitting diode De are formed in each pixel regionof the display area A1 on the substrate 110, and the encapsulation layer190 is formed to cover them.

Meanwhile, a gate driver 610 is provided in a first section of thenon-display area A2 on the substrate 110. The gate lines GL areconnected to the gate driver 610 and receive scan signals. The gatedriver 610 may be configured as a gate-in-panel (GIP) type in which itscomponents are formed through the same processes as the elements of thedisplay area A1.

Further, a data driver 630 is attached to a second section of thenon-display area A2 on the substrate 110. The data lines DL areconnected to the data driver 630 and receive data signals.

Then, the piezoelectric element 200 is disposed on the display panel100. The piezoelectric element 200 includes the lower electrode 220, theupper electrode 240, and the piezoelectric layer 230 between the lowerelectrode 220 and the upper electrode 240.

Here, the piezoelectric layer 230 may have an area corresponding to thelower electrode 220 or the upper electrode 240.

The lower electrode 220 and the upper electrode 240 have substantiallythe same area, and the area of each of the lower electrode 220 and theupper electrode 240 is larger than the display area A1. Therefore, thelower electrode 220 and the upper electrode 240 are disposed not only inthe display area A1 but also partially in the non-display area A2. Eachof the lower electrode 220 and the upper electrode 240 may have aprotrusion in the non-display area A2. The protrusion of the lowerelectrode 220 and the protrusion of the upper electrode 240 are spacedapart from each other and are connected to the rectifying circuit 260formed in the non-display area A2. The rectifying circuit 260 has theconfiguration of FIG. 2 and FIG. 3 .

Here, although the rectifying circuit 260 is illustrated as being formedin the non-display area A2 corresponding to an upper left corner of thesubstrate 110, but the position of the rectifying circuit 260 is notlimited thereto. The rectifying circuit 260 may be formed in anyposition of the non-display area A2. For example, the rectifying circuit260 may be formed in an upper right corner, a lower right corner or alower left corner of the substrate 110 corresponding to the non-displayarea A2.

The first buffer layer 210 is formed under the lower electrode 220, andthe second buffer layer 250 is formed on the upper electrode 240. Thesecond buffer layer 250 may have a larger area than each of the lowerand upper electrodes 220 and 240. In addition, the first buffer layer210 may have the same area as the second buffer layer 250.

Next, the touch panel 300 is disposed on the piezoelectric element 200.The touch panel 300 includes transmitting lines and receiving linesformed in the display area A1. Here, the transmitting lines and thereceiving lines cross each other to form mutual capacitors. Eachtransmitting line includes a plurality of transmitting electrodes 332connected to each other in the first direction, and each receiving lineincludes a plurality of receiving electrodes 334 connected to each otherin the second direction. Each transmitting electrode 332 and eachreceiving electrode may have a rhombus shape, but is not limitedthereto.

In addition, the touch panel 300 includes first routing lines 331 andsecond routing lines 333 formed in the non-display area A2. The firstrouting lines 331 are connected to the transmitting lines, and thesecond routing lines 333 are connected to the receiving lines.

The first and second routing lines 331 and 333 are connected to a touchdriver 640, which is attached to a third section of the non-display areaA2 on the substrate 110. Therefore, the first routing line 331 transfersa touch driving voltage from the touch driver 640 to the transmittingline, and the second routing line 333 transfers a touch sensing voltagefrom the receiving line to the touch driver 640.

Meanwhile, the polarizing plate 400 and the cover window 500 may bedisposed on the touch panel 300.

In the display device according to the first embodiment of the presentdisclosure, when a touch of a user is performed, the capacitance of themutual capacitor is varied, and the touch sensing voltage is changed.The touch driver 640 analyzes the touch sensing voltage and detects atouch point.

Moreover, a force is applied to the piezoelectric element 200 by thetouch of the user. Thus, a change in polarization occurs due to themechanical fluctuation of the piezoelectric material, and this causes apotential difference to generate the electrical energy. The electricalenergy is stored in a battery (not shown) through the rectifying circuit260. Accordingly, by changing the mechanical energy by the touch intothe electrical energy and using it, the power efficiency of the displaydevice may be improved.

The configuration of a display device according to the first embodimentof the present disclosure including a piezoelectric element will bedescribed in more detail with reference to FIG. 5 .

FIG. 5 is a schematic cross-sectional view of a display device includinga piezoelectric element according to the first embodiment of the presentdisclosure and corresponds to the line V-V′ of FIG. 4 . Here, anelectroluminescent display panel is used as an example of the displaypanel, but the present disclosure is not limited thereto.

In FIG. 5 , the display device according to the first embodiment of thepresent disclosure includes a display panel 100, a piezoelectric element200, a touch panel 300, a polarizing plate 400, and a cover window 500.

More particularly, a display area A1, which includes a plurality ofpixel regions and displays an image, and a non-display area A2, whichsurrounds the display area A1, are defined on a substrate 110 of thedisplay panel 100.

A semiconductor layer 122 is formed in the display area A1 on thesubstrate 110 and is patterned to correspond to each pixel region. Thesubstrate 110 may be a glass substrate or a plastic substrate. Forexample, polyimide may be used for the plastic substrate, but is notlimited thereto.

The semiconductor layer 122 may be formed of polycrystalline silicon,and in this case, both ends of the semiconductor layer 122 may be dopedwith impurities.

Meanwhile, a buffer layer (not shown) may be further formed between thesubstrate 110 and the semiconductor layer 122. The buffer layer may beformed of an inorganic insulating material such as silicon oxide (SiO₂)or silicon nitride (SiNx) and may be a single layer or a multiple layer.

A gate insulating layer 130 of an insulating material is formed on thesemiconductor layer 122 substantially all over the substrate 110. Thegate insulating layer 130 may be formed of an inorganic insulatingmaterial such as silicon oxide (SiO₂) or silicon nitride (SiNx).

A gate electrode 132 of a conductive material such as metal is formed onthe gate insulating layer 130 corresponding to a center of thesemiconductor layer 122. In addition, a gate line (not shown) and afirst capacitor electrode (not shown) may be formed on the gateinsulating layer 130. The gate line extends in a first direction, andthe first capacitor electrode is connected to the gate electrode 132.

Meanwhile, in the first embodiment of the present disclosure, althoughthe gate insulating layer 130 is formed substantially all over thesubstrate 110, the gate insulating layer 130 may be patterned to havethe same shape as the gate electrode 132.

An interlayer insulating layer 140 of an insulating material is formedon the gate electrode 132 substantially all over the substrate 110. Theinterlayer insulating layer 140 may be formed of an inorganic insulatingmaterial such as silicon oxide (SiO₂) or silicon nitride (SiNx) or anorganic insulating material such as photo acryl or benzocyclobutene.

The interlayer insulating layer 140 has first and second contact holes140 a and 140 b exposing top surfaces of the both ends of thesemiconductor layer 122. The first and second contact holes 140 a and140 b are disposed at both sides of the gate electrode 132 and arespaced apart from the gate electrode 132. Here, the first and secondcontact holes 140 a and 140 b are formed in the gate insulating layer130. Alternatively, when the gate insulating layer 130 is patterned tohave the same shape as the gate electrode 132, the first and secondcontact holes 140 a and 140 b are formed only in the interlayerinsulating layer 140.

Source and drain electrodes 142 and 144 of a conductive material such asmetal are formed on the interlayer insulating layer 140. In addition, adata line (not shown), a power line (not shown) and a second capacitorelectrode (not shown) may be formed on the interlayer insulating layer140.

The source and drain electrodes 142 and 144 are spaced apart from eachother with the gate electrode 132 disposed therebetween. The source anddrain electrodes 142 and 144 contact the both ends of the semiconductorlayer 122 through the first and second contact holes 140 a and 140 b,respectively. Although not shown in the figure, the data line extends ina second direction and crosses the gate line to define each pixelregion. The power line for supplying high potential voltage is spacedapart from the data line. The second capacitor electrode is connectedthe drain electrode 144 and overlaps the first capacitor to form astorage capacitor with the interlayer insulating layer 140 therebetweenas a dielectric. Alternatively, the first capacitor electrode may beconnected to the drain electrode 144, and the second capacitor electrodemay be connected to the gate electrode 132.

In the meantime, the semiconductor layer 122, the gate electrode 132,and the source and drain electrodes 142 and 144 constitute a thin filmtransistor T. Here, the thin film transistor T may have a coplanarstructure in which the gate electrode 132 and the source and drainelectrodes 142 and 144 are disposed at one side of the semiconductorlayer 122, that is, over the semiconductor layer 122, but is not limitedthereto.

The thin film transistor T corresponds to a driving thin filmtransistor. A switching thin film transistor (not shown) having the samestructure as the driving thin film transistor T may be further formed ineach pixel region on the substrate 110. At this time, the gate electrode132 of the driving thin film transistor T may be connected to a drainelectrode (not shown) of the switching thin film transistor, and thesource electrode 142 of the driving thin film transistor T may beconnected to the power line (not shown). In addition, a gate electrode(not shown) and a source electrode (not shown) of the switching thinfilm transistor may be connected to the gate line and the data line,respectively.

Meanwhile, one or more sensing thin film transistors having the samestructure as the driving thin film transistor T may be further formed ineach pixel region on the substrate 110, but is not limited thereto.

An overcoat layer 150 of an insulating material is formed on the sourceand drain electrodes 142 and 144 substantially all over the substrate110. The overcoat layer 150 may be formed of an organic insulatingmaterial such as photo acryl or benzocyclobutene. The overcoat layer 150may have a flat top surface.

In the meantime, an insulating layer may be further formed under theovercoat layer 150. The insulating layer may be formed of an inorganicinsulating material such as silicon oxide (SiO₂) or silicon nitride(SiNx).

The overcoat layer 150 has a drain contact hole 150 a exposing the drainelectrode 144. Here, the drain contact hole 150 a may be spaced apartfrom the second contact hole 140 b. Alternatively, the drain contacthole 150 a may be formed directly over the second contact hole 140 b.

A first electrode 160 of a conductive material having a relatively highwork function is formed on the overcoat layer 150. The first electrode160 is formed in each pixel region and contacts the drain electrode 144through the drain contact hole 150 a. For example, the first electrode160 may be formed of a transparent conductive material such as indiumtin oxide (ITO) or indium zinc oxide (IZO), but is not limited thereto.

Meanwhile, the electroluminescent display device 100 of the displaydevice according to the first embodiment of the present disclosure maybe a top emission type in which light of a light-emitting diode isoutput toward a direction opposite the substrate 110. Accordingly, thefirst electrode 160 may further include a reflective electrode or areflective layer, which is formed of a metal material having relativelyhigh reflectance, under the transparent conductive material layer. Forexample, the reflective electrode or the reflective layer may be formedof aluminum-palladium-copper (APC) alloy or silver (Ag). At this time,the first electrode 160 may have a triple-layered structure ofITO/APC/ITO or ITO/Ag/ITO, but is not limited thereto.

A bank 162 of an insulating material is formed on the first electrode160. The bank 162 overlaps edges of the first electrode 160, covers theedges of the first electrode 160, and exposes a central portion of thefirst electrode 160. The bank 162 may be formed of an organic insulatingmaterial having a hydrophobic property. Alternatively, the bank 162 maybe formed of an organic insulating material having a hydrophilicproperty and may be treated to have a hydrophobic property. However, thepresent disclosure is not limited thereto. Meanwhile, a bank having ahydrophilic property may be further formed under the bank 162.

Next, a light-emitting layer 170 is formed on the first electrode 160exposed by the bank 162.

Although not shown in the figure, the light-emitting layer 170 mayinclude a first charge auxiliary layer, a light-emitting material layerand a second charge auxiliary layer sequentially disposed on the firstelectrode 160. The light-emitting material layer may be formed of anyone of red, green and blue luminescent materials, but is not limitedthereto. The luminescent material may be an organic luminescent materialsuch as a phosphorescent compound or a fluorescent compound or may be aninorganic luminescent material such as a quantum dot.

The first charge auxiliary layer may be a hole auxiliary layer, and thehole auxiliary layer may include at least one of a hole injecting layer(HIL) and a hole transporting layer (HTL). In addition, the secondcharge auxiliary layer may be an electron auxiliary layer, and theelectron auxiliary layer may include at least one of an electroninjecting layer (EIL) and an electron transporting layer (ETL). However,the present disclosure is not limited thereto, and other variations arepossible.

Here, the light-emitting layer 170 may be formed through a solutionprocess. Thus, the process may be simplified and a display device with alarge size and high resolution may be provided. A spin coating method,an ink jet printing method, or a screen printing method may be used asthe solution process, but the present disclosure is not limited theretoand other variations are possible. When the solution is dried, a dryingspeed of a solvent in a region adjacent to the bank 162 is differentfrom that in other regions. Therefore, a height of the light-emittinglayer 170 in the region adjacent to the bank 162 may rise as it getscloser to the bank 162.

Alternatively, the light-emitting layer 170 may be formed through avacuum evaporation process, but is not limited thereto.

A second electrode 180 of a conductive material having a relatively lowwork function is formed on the light-emitting layer 170 substantiallyall over the display area A1. The second electrode 180 may be formed ofaluminum (Al), magnesium (Mg), silver (Ag), or an alloy thereof. Thesecond electrode 180 may have a relatively thin thickness such thatlight from the light-emitting layer 170 may be transmitted therethrough.Alternatively, the second electrode 180 may be formed of a transparentconductive material such as indium-gallium-oxide (IGO), but is notlimited thereto.

The first electrode 160, the light-emitting layer 170 and the secondelectrode 180 constitute a light-emitting diode De. The first electrode160 may serve as an anode, and the second electrode 180 may serve as acathode, but is not limited thereto.

As described above, the electroluminescent display device 100 accordingto the first embodiment of the present disclosure may be a top emissiontype in which light from the light-emitting layer 170 of thelight-emitting diode De is output toward a direction opposite thesubstrate 110, that is, output to the outside through the secondelectrode 180. The top emission type display device may have a wideremission area than a bottom emission type display device of the samesize, to thereby improve luminance and reduce power consumption.

At this time, the light-emitting diode De of each pixel region may havean element thickness for a micro-cavity effect corresponding to awavelength of the emitted light, thereby increasing the lightefficiency.

Next, an encapsulation layer 190 may be formed on the second electrode180 substantially all over the substrate 110 to block moisture or oxygenintroduced from the outside, thereby protecting the light-emitting diodeDe. The encapsulation layer 190 may be formed of UV sealant or fritsealant. Alternatively, the encapsulation layer 190 may includeinorganic layers and organic layers alternately stacked.

Meanwhile, a rectifying circuit 260 is formed in the non-display area A2on the substrate 110. The rectifying circuit 260 includes asemiconductor pattern 262, an anode 264 and a cathode 266. Here, thecathode 266 may be exposed to the outside and connected to a battery(not shown). Alternatively, the anode 264 may be exposed to the outsideand connected to the battery.

The semiconductor pattern 262 includes a P-type semiconductor region 262a and an N-type semiconductor region 262 b, and one of the P-typesemiconductor region 262 a and the N-type semiconductor region 262 b maybe formed of the same material through the same process as thesemiconductor layer 122 of the display area A1. For example, the P-typesemiconductor region 262 a may be formed of the same material throughthe same process as the semiconductor layer 122, but is not limitedthereto.

In addition, the anode 264 and the cathode 266 may be formed of the samematerial through the same process as the gate electrode 132 of thedisplay area A1. In this case, the gate insulating layer 130 may havecontact holes exposing the P-type semiconductor region 262 a and theN-type semiconductor region 262 b, and the anode 264 and the cathode 266may contact the P-type semiconductor region 262 a and the N-typesemiconductor region 262 b through the contact holes, respectively.

Alternatively, the anode 264 and the cathode 266 may be formed of thesame material through the same process as the source and drainelectrodes 142 and 144 of the display area A1. In this case, theinterlayer insulating layer 140 may have contact holes exposing theP-type semiconductor region 262 a and the N-type semiconductor region262 b, and the anode 264 and the cathode 266 may contact the P-typesemiconductor region 262 a and the N-type semiconductor region 262 bthrough the contact holes, respectively.

However, the present disclosure is not limited thereto. For example, theanode 264 and the cathode 266 may be formed in a layer different fromthe gate electrode 122 or the source and drain electrodes 142 and 144and may be formed in different layers from each other.

In addition, the P-type semiconductor region 262 a and the N-typesemiconductor region 262 b may be formed of the same material throughthe same process as an element of the gate driver 610 of FIG. 4 and maybe formed through an additional process.

Next, a piezoelectric element 200 is formed on the encapsulation layer190. The piezoelectric element 200 includes first and second bufferlayers 210 and 250, a lower electrode 220, an upper electrode 240, and apiezoelectric layer 230.

More particularly, the first buffer layer 210 is formed on theencapsulation layer 190 substantially all over the substrate 110. Thefirst buffer layer 210 may be formed of a transparent insulatingmaterial. For example, the first buffer layer 210 may be formed of aninorganic insulating material such as silicon oxide (SiO₂) or siliconnitride (SiNx). Alternatively, the first buffer layer 210 may be formedof an organic insulating material such as photo acryl, but is notlimited thereto.

The first buffer layer 210 has a contact hole exposing the anode 264 inthe non-display area A2. At this time, the contact hole is also formedin the encapsulation layer 190, the overcoat layer 150 and theinterlayer insulating layer 140. In addition, although not shown in thefigure, the first buffer layer 210 may have a contact hole exposinganother cathode or another anode.

The lower electrode 220 is formed on the first buffer layer 210substantially all over the substrate 110. The lower electrode 220contacts the anode 264 through the contact hole of the first bufferlayer 210 in the non-display area A2. The lower electrode 220 may beformed of a transparent conductive material. For example, the lowerelectrode 220 may be formed of indium tin oxide (ITO) or indium zincoxide (IZO), but is not limited thereto.

The piezoelectric layer 230 is formed on the lower electrode 220substantially all over the substrate 110. It is preferable that thepiezoelectric layer 230 is formed of a transparent piezoelectricpolymer.

The upper electrode 240 is formed on the piezoelectric layer 230substantially all over the substrate 110. The upper electrode 240 may beformed of a transparent conductive material. For example, the upperelectrode 240 may be formed of indium tin oxide (ITO) or indium zincoxide (IZO), but is not limited thereto.

Although not shown in the figure, the upper electrode 240 may contactanother cathode or another anode through the contact hole of the firstbuffer layer 210 exposing another cathode or another anode in thenon-display area A2.

Next, the second buffer layer 250 is formed on the upper electrode 240substantially all over the substrate 110. The second buffer layer 250may be formed of a transparent insulating material. For example, thesecond buffer layer 250 may be formed of an inorganic insulatingmaterial such as silicon oxide (SiO₂) or silicon nitride (SiNx).Alternatively, the second buffer layer 250 may be formed of an organicinsulating material such as photo acryl, but is not limited thereto.

The second buffer layer 250 may cover side surfaces of the lowerelectrode 220, the piezoelectric layer 230 and the upper electrode 240and may contact the first buffer layer 210 in the non-display area A2.

Next, the touch panel 300 is disposed on the piezoelectric element 200.The touch panel 300 may include transmitting electrodes 332, receivingelectrodes 334 and bridges 312.

More particularly, the bridges 312 are formed in the display area A1 onthe piezoelectric element 200, and a first insulating layer 320 isformed on the bridges 312 substantially all over the substrate 110. Thebridges 312 may be formed of a conductive material such as metal.Alternatively, the bridges 312 may be formed of a transparent conductivematerial, but is not limited thereto.

The first insulating layer 320 may be formed of an inorganic insulatingmaterial such as silicon oxide (SiO₂) or silicon nitride (SiNx). Thefirst insulating layer 320 has first and second touch contact holes 320a and 320 b exposing both ends of each bridge 312 in the display areaA1.

The transmitting electrodes 332 and the receiving electrodes 334 areformed in the display area A1 on the first insulating layer 320. Thetransmitting electrodes 332 and the receiving electrodes 334 may beformed of a transparent conductive material. Here, the transmittingelectrode 332 contacts the bridge 312 through the first and second touchcontact holes 320 a and 320 b. Accordingly, adjacent transmittingelectrodes 332 are connected to each other through the bridge 312 in thefirst direction to form a transmitting line.

Meanwhile, although not shown in the figure, the receiving electrode 334may be connected to another receiving electrode 334 adjacent thereto andmay be formed as one body. The receiving electrodes 334 are connected toeach other in the second direction to form a receiving line. However,the present disclosure is not limited thereto.

Alternatively, adjacent receiving electrodes 334 may be connected toeach other through a bridge, and adjacent transmitting electrodes 332may be formed as one body.

A second insulating layer 340 is formed on the transmitting electrodes332 and the receiving electrodes 334 substantially all over thesubstrate 110. The second insulating layer 340 may be formed of aninorganic insulating material such as silicon oxide (SiO₂) or siliconnitride (SiNx).

Next, the polarizing plate 400 is disposed on the touch panel 300. Thepolarizing plate 400 may be a circular polarizing plate which includes alinear polarizer and a quarter wave plate and changes linearly polarizedlight into circularly polarized light and circularly polarized lightinto linearly polarized light. The polarizing plate 400 may improve thecontrast ratio by blocking external light from being outputted afterbeing reflected at the display panel 100.

The cover window 500 is disposed on the polarizing plate 400. The coverwindow 500 protects the display panel 100 from the external impacts. Thecover window 500 may be formed of glass or plastic, but is not limitedthereto.

As described above, in the display device according to the firstembodiment of the present disclosure, by providing the piezoelectricelement 200 between the display panel 100 and the touch panel 300, themechanical energy by the touch is changed into the electrical energy andused.

FIG. 6 and FIG. 7 are plan views schematically illustrating electrodestructures of a piezoelectric element according to the first embodimentof the present disclosure.

In FIG. 6 , each of the lower and upper electrodes 220 and 240 and thepiezoelectric layer 230 of the piezoelectric element may be configuredas one pattern with respect to an entire surface of the substrate 110,and one rectifying circuit 260 may be provided at one side of thesubstrate 110.

Alternatively, in FIG. 7 , each of the lower and upper electrodes 220and 240 of the piezoelectric element may be divided into first, second,third and fourth patterns 222, 224, 226, 228, 242, 244, 246 and 248, andthe piezoelectric layer 230 may be configured as one pattern withrespect to an entire surface of the substrate 110. In addition, first,second, third and fourth rectifying circuits 260 a, 260 b, 260 c and 260d may be provided at four corners of the substrate 110 and may beconnected to the first, second, third and fourth patterns 222, 224, 226,228, 242, 244, 246 and 248, respectively. The configuration of FIG. 7may reduce a distance between an area where a touch occurs and therectifying circuit as compared with the configuration of FIG. 6 , andthe energy harvesting efficiency may be increased. It is to be notedthat the number of the divided patterns of each of the lower and upperelectrodes 220 and 240 may also be two, three, five or more, and thepresent disclosure is not limited thereto. In addition, there may betwo, three, five or more rectifying circuits, which may be disposed atany other locations in addition to the corners, and the presentdisclosure is not limited thereto.

At this time, the piezoelectric layer 230 may be divided into four, butis not limited thereto.

Second Embodiment

FIG. 8 is a cross-sectional view schematically illustrating a displaydevice according to a second embodiment of the present disclosure. Thesecond embodiment has the same configuration as the first embodimentexcept for the position of the piezoelectric element. The same parts asthe first embodiment will be designated by the same references, andexplanation for the same parts will be shortened or omitted.

In FIG. 8 , the display device according to the second embodiment of thepresent disclosure includes a display panel 100, a polarizing plate 400on the display panel 100, a piezoelectric element 200 on the polarizingplate 400, a touch panel 300 on the piezoelectric element 200, and acover window 500 on the touch panel 300.

The piezoelectric element 200 according to the second embodiment of thepresent disclosure may be formed directly on an upper surface of thepolarizing plate 400 or may be formed directly on a lower surface of thetouch panel 300. A piezoelectric layer 230 of the piezoelectric element200, beneficially, may be formed of a transparent piezoelectric polymer.

For example, the piezoelectric polymer may be PVDF(polyvinylidenefluoride), P(VDF-TrFE)(polyvinylidene fluoride-co-trifluoroethylene),P(VDF-TrFE-CFE)(poly(vinylidenefluoride-co-triluoroethylene-chlorofluoroethylene),P(VDF-TrFE-CTFE)(poly(vinylidene fluoride-co-triluoroethylene-chlorotrifluoroethylene), PVDF doped with carbonnanotubes, or a phosphazene-based polymer, but is not limited thereto.Here, poly bis(trifluoroethoxy) phosphazene may be used as thephosphazene-based polymer.

While the polarizing plate 400 is disposed between the touch panel 300and the cover window 500 in the first embodiment of the presentdisclosure, the polarizing plate 400 is disposed between the displaypanel 100 and the piezoelectric element 200 in the second embodiment.

In the display device according to the second embodiment, since thepiezoelectric element 200 is disposed closer to the cover window 500than the first embodiment, deformation due to a touch may further occur,thereby increasing the energy harvesting efficiency.

Third Embodiment

FIG. 9 is a cross-sectional view schematically illustrating a displaydevice according to a third embodiment of the present disclosure. Thethird embodiment has the same configuration as the first embodimentexcept for the position of the piezoelectric element. The same parts asthe first embodiment will be designated by the same references, andexplanation for the same parts will be shortened or omitted.

In FIG. 9 , the display device according to the third embodiment of thepresent disclosure includes a display panel 100, a touch panel 300 onthe display panel 100, a polarizing plate 400 on the touch panel 300,and a cover window 500 on the polarizing plate 400. In addition, thedisplay device further includes a piezoelectric element 200 under thedisplay panel 100.

The piezoelectric element 200 according to the third embodiment of thepresent disclosure may be formed directly on a lower surface of thesubstrate 110 of the display panel 100. Since the piezoelectric element200 is disposed under the display panel 100 where an image is notdisplayed, a piezoelectric layer 230 of the piezoelectric element 200may be formed of an opaque piezoelectric ceramic or an opaqueorganic-inorganic complex in addition to a transparent piezoelectricpolymer.

For example, the piezoelectric polymer may be PVDF(polyvinylidenefluoride), P(VDF-TrFE)(polyvinylidene fluoride-co-trifluoroethylene),P(VDF-TrFE-CFE)(poly(vinylidenefluoride-co-triluoroethylene-chlorofluoroethylene),P(VDF-TrFE-CTFE)(poly(vinylidene fluoride-co-triluoroethylene-chlorotrifluoroethylene), PVDF doped with carbonnanotubes, or a phosphazene-based polymer, but is not limited thereto.Here, poly bis(trifluoroethoxy) phosphazene may be used as thephosphazene-based polymer.

In addition, the piezoelectric ceramic may be PbZrTiO3 (PZT, LeadZirconium Titanate), Pb(MgNb)—PbZrTiO3, PNN-PT (Pb(NiNb)—PbTiO3), orPLZT (PbLaZrTiO3). Alternatively, the piezoelectric ceramic may beBaTiO3 (BTO, barium Titanate) or KNaNbO3 (KNN, kalium natrium niobate).

Meanwhile, the organic-inorganic complex may include the above-mentionedpiezoelectric ceramic and a polymer. Here, the polymer may be one of thepiezoelectric polymers described above or may be a non-piezoelectricpolymer such as epoxy, polyimide or polyurethane.

In the display device according to the third embodiment, since thepiezoelectric element 200 is disposed under the display panel 100, thebrightness of the display device may be maximized, and there is anadvantage that the piezoelectric material may be widely chosen ascompared with the first and second embodiments.

Fourth Embodiment

FIG. 10 is a cross-sectional view schematically illustrating a displaydevice according to a fourth embodiment of the present disclosure. Thefourth embodiment has the same configuration as the first embodimentexcept for the position of the piezoelectric element. The same parts asthe first embodiment will be designated by the same references, andexplanation for the same parts will be shortened or omitted.

In FIG. 10 , the display device according to the fourth embodiment ofthe present disclosure includes a display panel 100, a touch panel 300on the display panel 100, a polarizing plate 400 on the touch panel 300,and a cover window 500 on the polarizing plate 400. In addition, thedisplay device further includes a piezoelectric element 200 under thedisplay panel 100.

The piezoelectric element 200 according to the fourth embodiment of thepresent disclosure includes a base film 270, a first buffer layer 210, alower electrode 220, a piezoelectric layer 230, an upper electrode 240,and a second buffer layer 250. The first buffer layer 210, the lowerelectrode 220, the piezoelectric layer 230, the upper electrode 240, andthe second buffer layer 250 are sequentially disposed on a first surfaceof the base film 270. In addition, a rectifying circuit 260 is formed onthe first surface of the base film 270. Here, the rectifying circuit 260may be disposed on the first buffer layer 210, and the second bufferlayer 250 may cover a part of the rectifying circuit 260.

The piezoelectric element 200 may be attached to the display panel 100such that a second surface of the base film 270 may contact a lowersurface of the substrate 110 of the display panel 100. At this time, thebase film 270 may be attached to the lower surface of the substrate 110by an adhesive.

Meanwhile, a battery 800 may be disposed under the piezoelectric element200.

Since the piezoelectric element 200 is disposed under the display panel100 where an image is not displayed, a piezoelectric layer 230 of thepiezoelectric element 200 may be formed of an opaque piezoelectricceramic or an opaque organic-inorganic complex in addition to atransparent piezoelectric polymer.

For example, the piezoelectric polymer may be PVDF(polyvinylidenefluoride), P(VDF-TrFE)(polyvinylidene fluoride-co-trifluoroethylene),P(VDF-TrFE-CFE)(poly(vinylidenefluoride-co-triluoroethylene-chlorofluoroethylene),P(VDF-TrFE-CTFE)(poly(vinylidene fluoride-co-triluoroethylene-chlorotrifluoroethylene), PVDF doped with carbonnanotubes, or a phosphazene-based polymer, but is not limited thereto.Here, poly bis(trifluoroethoxy) phosphazene may be used as thephosphazene-based polymer.

In addition, the piezoelectric ceramic may be PbZrTiO3 (PZT, LeadZirconium Titanate), Pb(MgNb)—PbZrTiO3, PNN-PT (Pb(NiNb)—PbTiO3), orPLZT (PbLaZrTiO3). Alternatively, the piezoelectric ceramic may beBaTiO3 (BTO, barium Titanate) or KNaNbO3 (KNN, kalium natrium niobate).

Meanwhile, the organic-inorganic complex may include the above-mentionedpiezoelectric ceramic and a polymer. Here, the polymer may be one of thepiezoelectric polymers described above or may be a non-piezoelectricpolymer such as epoxy, polyimide or polyurethane.

The display device according to the fourth embodiment may be variouslyapplied by implementing the piezoelectric element 200 as a film type.Since the rectifying circuit 260 is provided on the base film 270 of thepiezoelectric element 200, it is easy to connect the rectifying circuit260 and the battery 800.

In the present disclosure, by providing the piezoelectric element underthe touch panel, the mechanical energy is changed into the electricalenergy and is used. Accordingly, the power efficiency of the displaydevice may be improved.

At this time, the piezoelectric element is close to the cover window,and thus deformation due to the touch may further occur, therebyincreasing the efficiency.

In addition, the piezoelectric element is disposed under the displaypanel where an image is not displayed, the brightness of the displaydevice may be maximized, and the piezoelectric material may be widelychosen.

Meanwhile, by implementing the piezoelectric element as a film type, thedisplay device may be variously applied. By providing the rectifyingcircuit on the base film of the piezoelectric element, connecting therectifying circuit and the battery may be facilitated and the efficiencymay be increased.

It will be apparent to those skilled in the art that variousmodifications and variations may be made in the display device of thepresent disclosure without departing from the technical idea or scope ofthe disclosure. Thus, it is intended that the present disclosure coverthe modifications and variations of this disclosure provided they comewithin the scope of the appended claims and their equivalents.

What is claimed is:
 1. A display device, comprising: a thin filmtransistor over a substrate; an overcoat layer on the thin filmtransistor; a first electrode on the overcoat layer; a light-emittinglayer on the first electrode; a second electrode on the light-emittinglayer; an encapsulation layer on the second electrode; a piezoelectricelement over the encapsulation layer; a touch panel over thepiezoelectric element; and a polarizing plate over the encapsulationlayer, wherein the piezoelectric element includes an upper electrode, alower electrode, and a piezoelectric layer, wherein a display areadisplaying an image and a non-display area surrounding the display areaare defined on the substrate, and wherein each of the lower electrodeand the upper electrode has a larger area than a total area ofelectrodes of the touch panel formed in the display area.
 2. The displaydevice of claim 1, wherein the polarizing plate is disposed over thetouch panel or disposed between the piezoelectric element and theencapsulation layer.
 3. The display device of claim 1, wherein thepiezoelectric layer includes a piezoelectric polymer.
 4. The displaydevice of claim 3, wherein the piezoelectric polymer includespolyvinylidene fluoride (PVDF), polyvinylidenefluoride-co-trifluoroethylene (P(VDF-TrFE)), poly(vinylidenefluoride-co-triluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)),poly(vinylidene fluoride-co-triluoroethylene-chlorotrifluoroethylene)(P(VDF-TrFE-CTFE)), PVDF doped with carbon nanotubes, or aphosphazene-based polymer.
 5. The display device of claim 1, wherein thepiezoelectric element further includes a first buffer layer under thelower electrode and a second buffer layer on the upper electrode.
 6. Thedisplay device of claim 5, wherein the second buffer layer has a largerarea than each of the lower electrode and the upper electrode.
 7. Thedisplay device of claim 5, wherein the second buffer layer is in contactwith the first buffer layer in the non-display area.
 8. The displaydevice of claim 1, wherein the piezoelectric layer is interposed betweenthe lower electrode and the upper electrode, and one of the lowerelectrode and the upper electrode is disposed between the piezoelectriclayer and the touch panel.
 9. The display device of claim 1, whereineach of the lower electrode and the upper electrode is partiallydisposed in the non-display area.
 10. The display device of claim 1,further comprising a rectifying circuit connected to the piezoelectricelement and formed in the non-display area on the substrate.
 11. Thedisplay device of claim 10, wherein each of the lower electrode and theupper electrode is configured as one or more patterns with respect to anentire surface of the substrate.
 12. The display device of claim 11,wherein a number of the rectifying circuit corresponds to the number ofthe patterns of each of the lower electrode and the upper electrode. 13.The display device of claim 10, wherein the rectifying circuit includesa diode having an anode, a cathode, a P-type semiconductor, and anN-type semiconductor, the anode and the cathode are formed of a samematerial in a same layer as a gate electrode or source and drainelectrodes of the thin film transistor, and one of the P-typesemiconductor and the N-type semiconductor is formed of a same materialin a same layer as a semiconductor layer of the thin film transistor.14. The display device of claim 10, wherein each of the upper electrodeand the lower electrode has a protrusion in the non-display area, andthe protrusion of the lower electrode and the protrusion of the upperelectrode are spaced apart from each other and are electricallyconnected to the rectifying circuit formed in the non-display area. 15.The display device of claim 10, wherein the lower electrode is connectedto the rectifying circuit through a contact hole formed in theencapsulation layer and the overcoat layer.
 16. The display device ofclaim 1, wherein the piezoelectric layer includes a piezoelectricpolymer, a piezoelectric ceramic, or an organic-inorganic complexincluding a piezoelectric ceramic and a polymer.